The world No 1 disappointed with his form and meets Robin Soderling in the quarter-finals at Roland Garros today.
Rafael Nadal not confident on chances of a sixth French Open crown
Rafael Nadal does not believe he is currently playing well enough to win a sixth French Open championship this year.
The world No 1 reached the quarter-finals at Roland Garros with a 7-5, 6-3, 6-3 victory over Ivan Ljubicic yesterday, but again he was not at his best, especially in a very scrappy first set.
Nadal has been exceptionally candid in press conferences during the tournament, talking at length about his struggles with confidence and his game and the difficulties of staying at the top of men's tennis year after year.
The 24-year-old Spaniard said: "I am not confident. I am not playing well enough to win this tournament the way I played. That's the truth. You have to be realistic.
"We will see after tomorrow if I am ready to play at this level. I am going to try. But I won five times already here. I don't have an obligation to win six. I am going to try, for sure.
"Sometimes it's much more important to win when you are not playing that well than win when you are playing well, because winning when you are playing well, probably it is easier."
Ljubicic conceded that a first-serve percentage of 51 per cent did not give him a chance of upsetting Nadal.
"I think it wasn't a bad match from my side it's just that the serve was not there," he said.
"Without the serve against anybody it's tough, but against Rafa it's definitely almost impossible.
"But he played well at that moment and I think he played a really good second set. I think today's match is going to give him quite a lot of confidence."
Nadal will play Robin Soderling in the last eight in a repeat of last year's final after the fifth seed defeated France's Gilles Simon 6-2, 6-3, 7-6 yesterday.
The Swede, who reached the final in 2009, has eased through the draw largely unnoticed and demonstrated what a threat he could be to Nadal with some big hitting.
Juan Ignacio Chela reached the quarter-finals for the first time since 2004 with a 4-6, 6-2, 1-6, 7-6, 6-2 win to end the run of the qualifier Alejandro Falla.
The Argentinian said: "It was a really tough match. It's a surprise for me to be again in the quarter-finals."
In the women's competition, Victoria Azarenka remains the highest seed in the draw after reaching the quarter-finals with a 6-2, 6-3 win over Ekaterina Makarova.
The No 4 seed tomorrow will play the Chinese No 6 seed Li Na, who won six games in a row on her way to a 2-6, 6-1, 6-3 victory that ended the hopes of Petra Kvitova, the Czech Republic No 9 seed.